Atari 800 Service Manual

the different output devices, such as PIA chip, POKEY chip and the
CTIA chip.
Only four of the possible output selections are used. ( See Table 4-
3. ) The I/O Decoder is enabled by inputs on pins 4, 5, and 6; pin 4
input coming from the Memory Map Decoder (S6); pin 5 input coming the
Address Bus and pin 6 input coming from the Chip Select (CS) line.
The Binary Decode is provided by the Address Bus (A08, A09 and A10).
Table 4-3. I/O Decoder Select Lines
Enable/Pin Binary Decode
A
1
2
6
A
1
1
5
S
6
4
A
1
0
3
A
9
2
A
8
1
Active
Pin
Device
Selected
H L L L L L Y0 - 15 CTIA
H L L L L H Y1 - 14 Not Used
H L L L H L Y2 - 13 POKEY
H L L L H H Y3 - 12 PIA
H L L H L L Y4 - 11 Not Used
H L L H L H Y5 - 10 External
Select
Y6 - 9 Not Used
Y7 - 8 Not Used
ATARI Personal Computers 4-13
4.3.3 Motherboard Console System (800)

Atari 800 Specifications

General

Processor	MOS Technology 6502
Processor Speed	1.79 MHz
ROM	10 KB
Graphics	ANTIC and GTIA chips
Release Year	1979
Display Resolution	up to 320 x 192
Colors	128 colors
Sound	4 channels
Storage	Cartridge, cassette, floppy disk
Ports	Cartridge, serial, monitor
Operating System	Atari OS